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IICPE.2016.8079373

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Arduino Based Solar Powered Battery Charging
System For Rural SHS
Tarlochan Kaur, Jaimala Gambhir, Sanjay Kumar
Department of Electrical Engineering
PEC University of Technology
Chandigarh-160012, India
tarlochan.kaur@gmail.com, jaimalajindal@yahoo.com, sanjnitham@gmail.com
Abstract— Solar Energy is a clean and renewable power
resource and is on its way to high level penetration in the world
electricity energy basket. However, there are several challenges
associated with Solar Energy, like intermittency, limited dispatch
ability and non-storability. Non-storability in a standalone PV
system can be mitigated by incorporating energy storage devices
like battery to store the electrical energy produced by solar panel
when the sun is shining and to supply power when the sun is not
shining. Batteries are, therefore, one of the critical component in
the standalone PV system. And often the weakest link in PV
systems as it influences the maintenance cost and reliability of the
system. This paper involves designing and development of a low
cost, microcontroller based, solar powered battery charging
system. The developed system incorporates (i) MPPT (ii)
Arduino Uno interface for battery management functions
Arduino Uno interface , (iii) LCD display for information to the
user about the system regarding the systems overall capacity to
charge at any given time, (iv) data storage and incorporates
Wi-Fi module for remote surveillance and uploading live data
which can further be used for studying the health of the battery
and help in maintenance of battery. The developed solar
powered battery charging system for DC loads has been designed
for use in Solar Home Systems (SHS). The individual SHS can
be connected to form a low voltage DC micro grid for the
remotely located rural population for sustainable provision of
electric energy services.
Keywords— Battery; Charge controller; Arduino Uno; Solar
PV Panel
I. INTRODUCTION
Increasing energy demand, depleting fossil fuels, new load
types, rural electrification, energy security are some of the
drivers for power sector to embark on to a journey of
sustainable energies. Renewable energies will play a key role
in this journey. Solar Energy is expected to contribute to the
energy mix in a large measure because it is abundant and clean.
Solar PV systems involve no fuel cost, are silent in operation,
require less maintenance and have long life. In India the Solar
Mission is supported by MNRE and MoP. 100 GW of solar
power is envisaged by 2022. Out of this 40 GW of Rooftop PV
and 60 GW of Solar Thermal will be generated according to
report of JNNSM (Jawaharlal Nehru National Solar Mission)
MNRE, India. Decentralized Distributed Generation (DDG)
scheme envisage provision of electricity to villages from
conventional or renewable sources on a standalone basis [1]. In
order to provide access to electricity to rural population with
low energy consumption in remote and off grid areas, a low,
978-1-5090-4530-3/16/$31.00 ©2016 IEEE
voltage DC distribution network where in individual Solar
Home Systems (SHS) can be interconnected, is an attractive
option [2]. However such standalone renewable energy
solutions need energy storage devices for making the power
available without interruption over a number of days. Lead
acid batteries currently provide the best cost to benefit ratio
amongst various energy storage technologies [3]. In this paper
a low cost Arduino Uno based solar powered battery charging
system for SHS has been designed and developed.
II. CONVENTIONAL METHODS AND PROBLEMS
The major components in standalone solar PV system Solar
PV panels, batteries and power conditioning devices .The solar
PV panels produce DC power which was later on converted to
AC using converter devices. The use of power electronics
converters increase the complexity and decrease efficiency of
the power system [4]. Nowadays, increasing number of devices
which use DC, such as laptops, mobile phones and other power
electronic devices used in our daily life are being incorporated.
Such applications need to convert AC back to DC. This
conversion increases the losses and complexity of the power
system. This concept is particularly useful for rural and
sparsely populated areas where in low voltage DC network can
supply electricity generated by solar PV to cater to the load
constituting of LED lamps, DC fan, TV and mobile charging
stations. To improve the efficiency of such a power network,
instead of using multiple conversions, the whole power system
can be represented in figure 1. The DC based power system
helps to eliminate the requirement of converters systems,
reducing converter cost, power system complexity, improve
efficiency and reliability. The batteries are used to store the
energy from solar panels as an energy bank for emergency and
night hour usage in domestic and industrial applications. To
charge these batteries from the sun light rated amount of
current for rated time duration is required. If excess current is
supplied, the battery can be damaged. If battery is overcharged
or discharged for a long duration of time, batteries life span
will come down. The conventional battery chargers available in
market have limited features. And some time they do not
monitor the battery health properly, and may let the battery to
undergo deep discharge or overcharge. If a battery goes into
deep discharge, it is very difficult to recharge it using battery
charger since the electrode plates of battery will be fully
sulphated, resisting the charging.
Silicon, copper-indium selenide and amorphous silicon. The
efficiencies vary from 6% to 25%. A Mono crystalline silicon
PV cell has higher conversion efficiency (approx. 22%) as well
as higher cost. In this work mono crystalline Silicon panel is
used. Electrical characteristics of the PV Panel (Values at STC
(AM1.5, 1000W/m², 25°C))
Fig. 1. Block diagram of the proposed solar system
To charge a deep discharge battery, a large current to
reverse the chemical reactions which took place during
discharging is required.
•
Max Power Pmax : 50Wp +/-3%
•
Panel Voltage : 12 V
•
Nominal Current Imp : 2.77A
•
Nominal Voltage Vmp : 17.20V
•
Cell Efficiency : 17%
•
Open–Circuit Voltage Voc : 21.6 V
•
Module Efficiency : 14.6%
•
Short-Circuit Current Isc : 3.23 A
The I-V characteristic of solar cell under varying sunlight is
shown in Figure 3. The knee point where the dropping voltage
line meets the vertical power line shows the optimal power
available.
Fig. 2. Block diagram of the proposed solar system
If we supply huge current to a deep discharged battery,
battery will get damaged. And if we let a battery to be in
charging process for a long duration (over charging), gassing
of hydrogen and oxygen occurs at the electrode plates and
wash away the active material coated on the plates this again
leads failure of battery hence an intelligent battery charging
system is necessary to take care of these problems. In this
work, a low cost solar powered battery charger for DC loads
(DC lighting i.e. LEDs, DC gadgets like laptops, telephones,
satellite TV controllers etc.) has been designed and developed.
The developed system has the capability of logging and storing
data for remote surveillance, leading to better maintenance of
the battery, thereby increasing the life of the battery. Figure 2
gives the block diagram of the proposed system. The overall
solar PV standalone system consist of a solar panel, Arduino
interfaced MPPT charge controller, Wi- Fi module battery
bank, and load to deliver usable power to the end user [5,8].
III.
BASIC DESCRIPTION OF THE SYSTEM
A. PV Cell Chemisteries
The solar panel consist of a number of Si based PV cells
combined in series and in parallel depending on the required
voltage and the current. Presently the commonly used different
types of PV cells are polycrystalline Silicon, mono crystalline
Fig. 3. Standard I-V Characteristics of PV Cell
B. Batteries for Energy Storage
Energy storage devices are required for ‘power
applications’ and ‘energy applications’. In energy applications,
the discharging process of energy is slow as compared to
power applications and generally takes ten minutes to hours. In
case of power applications discharging of the stored energy
take place at very high rate, from seconds to minutes [7]. In
power applications the energy storage medium is flywheel,
battery, hydrogen and electrochemical capacitors (ECs). Most
common used energy storage technology is lead-acid battery
because of its main advantage over the other rechargeable
batteries is that power ratio is superior. Generally there are two
categories of lead–acid batteries flooded lead acid (FLA)
batteries and valve regulated lead-acid (VRLA). VRLA is
further categorized as Absorbed Glass Mat (AGM) and Gel.
VRLA batteries are also known as sealed batteries. Sealed
batteries, though costly, have the advantage of less
maintenance and longer life span. In the present work AGM
battery is used.
C. Charge Controller
A battery charging system is not complete without a
charge. Mainly it is type of regulator that prevents the batteries
from overcharging. The charge controller converts the
incoming DC voltage from the solar panels to the exact voltage
range suitable for battery charging. The charge controller unit
must work for the given range of the voltage and should cut
automatically if SPV voltage falls below desire value [13]. As
the intensity of light reduced, the charge controller
automatically turns off and switches on when adequate amount
of light is restored again. Most of the available charge
controllers can operate only on ideal lighting conditions. Due
to this shortcoming, the use of such charge controllers is
limited. The developed charge controller use maximum power
point tracking (MPPT) to track and adjust the voltage and
current to follow the maximum power with prevailing light
conditions. However, MPPT controllers are costly [8]. Figure 4
depicts the Tracking Algorithm of Maximum Power Point
Tracker used.
slowly decrease the current level when power bank is topped
off. The full capacity of the batteries is referred to as float
charging stage. The developed battery charger can be in one of
the following four states:
• On State: Is the charger state for solar power value in
between minimum solar power value and low solar
power value (minimum solar power < solar power <low
solar power) [12]. In this state, for bulk charging state
the solar watts input are very low but not so much low
to go into the off state. To get low amount of power
pulse width modulation is set to be 99.9%.
•
Bulk State: Is the charger state in which solar power is
greater than the minimum solar power. In this state, the
Peak Power Tracking algorithm is used for the bulk of
the battery charging by running the maximum amount
of current in the circuit that the solar panels are
generating into the battery.
• Float State: In this stage, voltage is rise till maximum
battery voltage is achieved . So this state is known as
float state. In this state, by adjusting the PWM value the
battery voltage is maintained at its maximum. If PWM
attain its 100%, then the battery is being drawn down
by some load because battery voltage can’t be kept at
maximum.
• Off State: When no power is generated by the solar
panels the charger goes into Off state (solar power <
minimum solar power). In this situation power from the
battery can reflect into the solar panel, so all the
MOSFETs are turned off to avoid this situation. If the
solar panel isn’t producing power then it’s probably
night time. Therefore, the load state will be on which
means that the load connected will take supply from the
battery and there is no supply from the solar panel. The
final code of the Arduino circuit used for MPPT was
developed.
D. DC to DC Converter
A DC-to-DC converter is required to increase (Boost) or
decrease (Buck) the input panel voltage to the required battery
level. The main parameters of the buck circuit are the inductor,
capacitor, and MOSFET. In this work IRFZ44N MOSFET is
used as a switch.
Fig. 4. Tracking Algorithm of Maximum Power Point Tracker.
Pulse width charge controller use high frequency pulses to
control the current from the source depending upon the state
of charge of battery. Pulse width charge controller checks the
magnitude and time of pulse to reduce battery overcharging.
During peak when the batteries are discharged a signal is
received by the PWM charger and full current pulses remain
continuous, as it becomes charged and this stage is called bulk
stage of charging.
Absorption is the next step of charging which occurs when
batteries are near to the full state of charge (SOC). The battery
bank voltage is held constant by the controller for certain
period of time. Further, the off time of the pulses increased to
E. Microcontroller
Arduino Uno (ATmega 328P) microcontroller is used as
easy to program. It has 14 digital input/output pins. Out of
these these 14 pins, 6 are used as PWM outputs and 6 are
used for analog inputs. It is powered by USB connection to
computer and has a reset button. Operating voltage is 5 V.
IV.
INTERFACE BETWEEN THE CONTROLLER AND
WI-FI MODULE
Wi-Fi module (ESP8266) is used to accomplish the
monitoring task. It is a self-contained SOC which stands for
(System on Chip) support integrated TCP/IP protocol stack
which provides any microcontroller with an access to any Wi-
Fi network. The ESP8266 is able to host or offload an
application from another application processor doing all Wi-Fi
networking functions. Every ESP8266 module comes preprogrammed with a firmware, AT command set, so we can
simply connect it to Arduino device and get about as much WiFi-ability as a Wi-Fi Shield offers. In this work, the data is sent
through AT commands from a computer to serial adapter by an
USB. The working of Wi-Fi module is tested with and
firmware installed in the ESP8266 module Arduino Uno, in
order to integrate in the main circuit (Fig. 5).
Fig. 7. Solar PV voltage Vs Time
The data can also be send to the locations of the nearest
solar tree system for the users’ smart phones. All this can lead
to a designing of a better, efficient, IoT (Internet of Things)
integrated and better connected PV systems. Table 1 gives the
list of main components used.
Table 1. List of component used
Component
Fig. 5. Interfacing of Wi-Fi module with Arduino
Firmware is basically a set of instructions uploaded directly
into the ESP8266 module by connecting it to the laptop
directly. For this, USB to TTL logic convertor has been used to
establish communication between the developed system and
Wi-Fi module. Flasher is then used to flash the firmware into
ESP module. Through AT commands, communication is
facilitated between the module and internet. After establishing
the connections, this circuit (Wi-Fi module) is implemented
into our main circuit (Fig. 6).
Solar PV Panel
Battery
Mosfet Driver
Buck Converter
Boost Converter
Load
Microcontroller
WI Fi Module
Specifications
Rated Power – 50W;
Cell Type – Monocrystalline;
Open Circuit Voltage: 21.6V; Short Circuit
Current: 3.23 A; Max. Power Voltage: 17.20 V
Absorbent Glass Mat (AGM) ;
Nominal Voltage :12V;
Internal Resistance- Fully Charged battery 770F30 mŸ
Gate drive supply - 10 to 20V;
VOFFSET - 600V (max)
VOUT - 10 - 20V; IO+/- - 130 mA / 270 mA
Resistance–220Ÿ;
Inductance–33micro Henry;
Capacitance– 0.1microFarads
Inductance – 90 micro Henry
Capacitance – 220 micro Farads
Lamp; Voltage – 12 V; Rated Power - 6W
Arduino Uno
ESP8266; Module operates at 3.3V; 240mA peak
current;
100M for max transmitting distance ;+20Dbm
power
Current and Voltage Sensors; LCD display
V. CONCLUSIONS
Fig. 6. Wi-F interfacing with main Circuit
Data Logging helps to gather data about solar PV system
and battery for many purposes. Figure 7 depicts variation of
PV voltage with time.
In this paper, design and development of a low cost Arduino
based Advance Solar powered Battery Charge Controller is
presented. The charging of battery is implemented using
MPPT algorithm. Thus extra energy harvest is obtained by
operating at PV peak power point instead of output voltage of
PV at any given time. The charge controller has an battery
management system in built along with LCD display and Wi Fi
module for data logging and storing. The in and out voltage
and current flow in the battery, the state of charge of battery
and cut off the battery when various limits are reached are
indicated by display. The developed battery charger will help
better monitoring of battery performance and reliability of the
system. It can also be used for remote surveillance of battery
connected to PV standalone systems.
ACKNOWLEDGMENT
The authors thankfully acknowledge Tata Power Delhi
Distribution Ltd., New Delhi for funding the project on
‘Design and development of Solar Powered Battery Charge
Controller”.
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